The present invention relates to packet-switched communications networks having a plurality of interconnected node stations each serving a plurality of user terminals, and more specifically to such a packet-switched communications network in which each of the node stations is capable of switching circuit-switched signals (non-burst signals).
In packet switching, the transmission medium of the network are occupied for as long as a packet propagates through it. For this reason packet-switched network is best suited for switching burst signals. By packetizing non-burst signals and incorporating a priority control scheme it is possible to integrate circuit-switched signals with packet-switched signals (burst signals) in a single network. However, the necessity to append addresses to each packet represents a substantial amount of overhead and significantly reduces the transmission efficiency.
U.S. Pat. No. 4,569,041 discloses an integrated circuit/packet switching system including a plurality of interconnected node stations each serving a plurality of user terminals. In this system, non-burst signals are sampled at 125 microseconds intervals and a plurality of such samples are stored in memory for a predetermined time interval to form a circuit-switched signal. A plurality of circuit-switched signals are carried on respective time slots of a fixed-length packet which is destined to the same node station. The overhead of the packet includes time slot numbers in addition to source and destination addresses. Although high efficiency switching can be achieved when connections are established from a given source node to the same destination node, multiple connections from a given source node to multiple destination nodes requires packets to be directed to respective destination nodes with a resultant decrease in the network switching efficiency. Furthermore, each node station must be provided with as many transmit buffers as there are destination nodes at a given instant of time.